Introduction to food webs

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Introduction to food webs

• 28 February 2006
• AWER 4500

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Food Webs
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Physiological processes that are essential to
food webs

• Photosynthesis
• Respiration
• Detrital processing (decomposition)
• In streams, completed in stages
• Invertebrates and bacteria
• Nutrient recycling

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Classification of organisms by functional
significance

• Autotrophs
• Photoautotrophs
• Chemoautotrophs
• Detritovores
• Herbivores
• Carnivores

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Allochthonousvs. Autochthonous
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A stream food web

• Algae and bacteria
• Invertebrates
• Fish, amphibians

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Biofilms

• Consists of many different organisms
• Periphyton (algae)
• Bacteria
• Protozoa
• Microinvertebrates
• Mucilage
• Low-lying community

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Benthic Primary Producers

• Different layers grow on a single substrate
• Macrophytes also may be important

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Lake food web
Light nutrients
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Pelagic Zone Organisms

• Bacterioplankton and protozoans
• Phytoplankton and cyanobacteria
• Zooplankton
• Fish and salamanders
• Zooplanktivores
• Benthivores
• Piscivores

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Food webs in lakes

• Primary Predators
• Zooplanktivorous fish
• Benthivorous fish
• Secondary Predators
• Piscivorous Fish
• Bears, birds, humans

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Food webs in lakes

• Microbial loop
• Analogous to biofilm in
• streams

Fig. 18.4 Representation of traditional views of
a pelagic food web and the microbial loop